Healthy river systems in the UK may boast equally vibrant populations of otters as typical coastal habitat, but riparian otters are usually harder to spot due to high levels of human and dog disturbance, dense vegetation and the fact that it is more challenging to see these mustelids hunting in fast moving rivers than on the sea.
Coastal otters frequent intertidal zones in search of blennies, eels, rockling, crabs and other crustaceans, and are easy to spot when on the shore.
Otter watching involves perseverance. On a river it is vital to check for signs during winter when the vegetation has died back.
These include spraint sites on exposed roots and stones, worn slides on muddy banks and tracks showing five webbed toes.
On the River Tay, where beavers have recently become abundant, otters make use of beaver-felled stumps as spraint sites; both species are seen in close proximity, usually with no conflict.
Do you have a wildlife question you’d like answered? Email your question to firstname.lastname@example.org or post it to Q&A, BBC Wildlife Magazine, Immediate Media Company, 2nd Floor, Tower House, Fairfax Street, Bristol, BS1 3BN